1. Field of the Invention
The present invention relates to a method for obtaining narrow tolerances of the accuracy to shape and size of a product rolled in a wire mill and/or bar mill with the use of at least two sizing stands of high stiffness which, with the exception of the last stand, are adjustable under load. The stands cooperate with means for detecting the geometrical data of the rolled product and relevant rolling-operation data of the product, as well as with a computer in which a signal is calculated from stored data and measured data, wherein the signal is used to correct the adjustment of at least one of the stands.
The present invention also relates to an apparatus for carrying out the above-described method.
2. Description of the Related Art
The automatic control of rolling trains, particularly for rolling sheet products, is known. In sheet rolling trains, for example, the thickness of the product is measured continuously or periodically and the roll gap of one or more roll stands of the rolling train is changed on the basis of the measurement in accordance with a mathematical algorithm in order to obtain a product of the desired thickness.
When rolling sections, control of the train is more complicated. The change in the roll gap has more influence than in the case of a sheet on the circumferential dimension of the section, i.e., the width of the section changes. Effects of changes of diameter in longitudinal direction, for instance due to eccentricity of the rolls, changes in temperature in the rolled product, and changes in tensile stress or wear, can only be insufficiently compensated. This is because, in the known methods for controlling section rolling mill trains, the geometrical data of the rolled product are detected in order to determine an optimum correction in a computer on the basis of the relevant rolling operating data stored therein. However, the detection of the geometrical data takes place only behind the last stand of the train. As a result, mistakes can only be compensated after they have already occurred, so that a considerable part of the rolled product produced cannot comply with the necessary tolerance values (Federal Republic of Germany 28 11 778).
Because of the detection of differences in tolerance only behind the finishing stand, higher demands had to be placed on the preliminary cross section, particularly if-as is also known-the group of finishing stands has been operated with two rigid grooves. The temperature differences over the length of the bar also had to be kept very small in order to achieve results which comply with the tolerance. Even if the finishing stand were made adjustable, it could not be prevented that errors could only be corrected after they had already occurred.